Harbaugh 'relentlessly positive' about team

SANTA CLARA, Calif. -- There's no doubt, Jim Harbaugh loves this time of year.

The colorful San Francisco 49ers' coach repeatedly referred to Thursday's start of training camp as a "rebirth." He said he is "relentlessly positive" and believes his team is up for the task of remaining one of the NFL’s elite teams.

"They are cheerful and undefeated," Harbaugh said of his team. "This is the least the unhappy team I’ve ever been around."

In other 49ers news:

Rookies Bruce Ellington, Marcus Martin and Aaron Lynch should all be able to practice fairly soon, according to Harbaugh. He said Ellington and Martin both got hurt doing individual football drills.

Harbaugh didn’t give a timetable for the return of running back Marcus Lattimore. The team is just being cautious and Lattimore has not sustained a new injury. Lattimore, a fourth-round pick in 2013, hasn't played since he suffered a devastating knee injury at South Carolina in 2012.

Harbaugh said the team did a great job in its conditioning test Wednesday. "They killed it. Knocked it out of the park. Great slam."

Tight end Garrett Celek is on the PUP with a back injury and the team doesn't know how serious it is. Celek will have to earn a spot on the 53-man roster.

The 49ers will likely use two locker rooms, at the new Levi's Stadium and at the team

s adjacent facility.

In this Insider piece, Mel Kiper and Mike SandoInsider believe Aldon Smith and Eric Reid are among the best under 25-year-old players in the NFL.